Dem Japanese... I like Korean better though. Not sure why, might be because it's new for me after that much anime..

What about albums/singles that are sold in multiple countries, (Japan, Thailand, Korea)

They're still either Japanese or Korean because that's the two languages they sing in, bar the couple of English songs
The Japanese thing just means the songs in Japanese, which means it's on one of their Japanese albums They have two Japanese albums, Girls & Peace being their second one.